Electron Microscopy of Oncocytomas and Carcinoid Tumors

Abstract

Numerous electron microscopical examinations of oncocytes and oncocytomas (Hamperl, 1931, 1936), particularly of the salivary glands, have shown that oncocytes differ from other epithelial cells in their excessive proliferation of abnormal mitochondria (Roth et al., 1962; Tandler and Shipkey, 1964; Balogh and Roth, 1965; McGavran, 1965; Hübner et al., 1965; Tandler, 1966; Kleinsasser et al., 1966; Hübner et al., 1967). The cytoplasm is filled wither with numerous oval mitochondria, in which most of the cristae are stacked closely together in the center, or with longitudinal mitochondria having transverse tubular cristae (Fig. 1). Occasionally, the mitochondria of the oncocytomas contain aggregated glycogen. Mitochondria found in oncocytes are often larger than normal ones. Giant mitochondria are almost invariably spherical and sometimes have inner membranes arranged in arcade like layers, suggestive of Romanesque arches. Obviously, this special architectural structure of the inner membranes serves to make the giant mitochondria structurally more stable.